Hydraulic muscle pump

ABSTRACT

This invention comprises four hydraulic muscle pumps connected to four hydraulic dynamic muscles in hermetically sealed pairs to transfer tensive forces from a local to a remote location for use in actuating the articulation section of a borescope or endoscope.

This is a division of U.S. application Ser. No. 357,806, filed May 30,1989, now U.S. Pat. No. 4,962,751.

BACKGROUND OF THE INVENTION

This invention relates to a liquid actuated traction system, and is moreparticularly concerned with a device which transfers a tensive force viaa closed liquid pressure system so as to apply at a remote location atensive force, to an object to be pulled.

The invention is also directed to a liquid or hydraulic pump which canbe incorporated within an elongated insertion tube of a borescope orlike device for actuating the articulation or steering section, so thatthe use of extremely long steering cables can be avoided.

A borescope is generally characterized as an elongated flexibleinsertion tube with a viewing head at its distal or forward end, and acontrol housing at its proximal end for controlling or steering theforward end. Such a borescope has a bendable-tube steering section orarticulation section at the distal end adjacent the viewing head. One ortwo pairs of control cables extend through the articulation section, andthen through the remainder of the flexible insertion tube. These cablesconnect with a steering control in the control section. One or bothpairs of these cables are differentially displaced to bend thearticulation section. The viewing head can thus be remotely oriented tofacilitate the inspection of an object. Borescopes are intended forvisual inspection of mechanical devices such as jet engines or turbines,where it would be difficult or impossible to examine the device'sinternal elements directly. The borescope needs to go into narrowtortuous passageways, and must observe similar bending and steeringconsiderations. In addition the pathway to the object can be quite long,and so it is often necessary that the borescope insertion tube befifteen meters or more in length.

Endoscopes are similar devices, but are intended to be inserted into abody cavity, such as the colon or esophagus, for visual investigation oftissues within the cavity.

A number of types of cable actuated articulation or steering mechanismsare known, and typical ones are discussed in U.S. Pat. Nos. 3,610,231;3,739,770; 3,583,393; 3,669,098; 3,779,151; and 4,347,837. Anothersteering mechanism is described in U.S. Pat. No. 4,700,693 having acommon assignee herewith.

The articulation mechanisms for those previously-proposed endoscopes andborescopes require that the cables have a significant amount of slack orplay because bends and coils in the insertion tube effectively shortenthe cables and because the articulation section bends at discrete pointsrather than follows a smooth curve. However, in both the borescope andendoscope, the articulation section must be bent rather precisely inorder to obtain the desired penetration without damaging delicate engineparts or injuring the patient's tissues. For these reasons cable tensionmust be limited and cable slack must be minimized. Where the insertiontube is long, extra cable slack is often included to accommodate theeven greater cable tightening due to the substantial coiling and bendingof the insertion tube through which the steering cables pass.

Also, when the cables are differentially displaced to effectarticulation, the cable displacement is not precisely reciprocal. Thatis, the motion of one cable is not the exact opposite of the other. Thisfact results in undesirable tensioning at some times, and at other timesproduces unwanted cable slack which can lead to imprecise steering.Coiling of the insertion tube can produce high tension in both cables ofa cable pair, which can lead to increased friction and damaging highforces on the cables and on the articulation section. If no measures aretaken to compensate for this, early failure can follow. Even when onlyone cable carries tension, coiling of the insertion tube can producesufficient friction on the cable to prevent articulation.

PRIOR ART

Ideally, the steering cables should be kept short to avoid the aboveproblems. To do this, the cables would have to terminate within theinsertion tube near the articulation section, and some mechanism to drawthe cables would be incorporated within the sheath of the insertiontube. Unfortunately, no known existing mechanism had been proposed forthis task until U.S. Pat. No. 4,794,912 issued Jan. 3, 1989. (Thispatent has a common assignee herewith.) This patent shows a method anddevice for overcoming many of the problems found in these priorborescope/endoscope steering mechanisms. Specifically, in the aforesaidpatent there is shown a fluid dynamic muscle mounted adjacent the distalend of the insertion tube which is actuated by pneumatic or hydraulicpressure supplied through small flexible tubes within the borescopeinsertion tube. The muscle is mounted adjacent the flexible portion ofthe endoscope/borescope so that the bending cables can be very short anddirect in the performance of their bending function without thelimitations and problems of the much longer cables referred to in theforegoing prior art.

Thus, as described and claimed in said patent, as fluid pressure isapplied to the fluid muscles in the distal end of the borescope, thetube is forced to bend in the desired direction to permit properviewing, without the problems of extremely long cables that flex,stretch, etc., as described above. This offers a distinct improvementover prior art and allows a much more accurate and precise positioningof the viewing end of the borescope within the cavity being inspected.

As shown in the foregoing patent, the pneumatic muscle system required asource of fluid power at the manipulating end of the borescope. This wasindicated in the subject patent as a joystick valve arrangement and apressure source such as an air compressor.

OBJECTS AND SUMMARY OF THE INVENTION

Since borescopes/endoscopes are frequently used at remote locations andin unusual situations where a readily available source of air orhydraulic pressure is not always possible, it became desirable toprovide a self-contained actuating system that took advantage of thefluid muscle previously disclosed without reintroducing thedisadvantages of the long, flexible actuating cables of the prior art.

Accordingly, it is an object of the present invention to provide aself-contained liquid actuated system for articulating borescopes,endoscopes, and the like.

It is another object of the present invention to provide a fluidpressure source for a fluid dynamic muscle actuator for the articulationsection of a borescope/endoscope.

It is a still further object of the present invention to provide aclosed loop hydraulic actuating system for hydraulic muscle actuation ofarticulation sections of borescopes that does not require any externalsource of power.

It is yet a further object of the present invention to provide ahydraulic transmission system for transforming mechanical pulling forceat a control, to hydraulic activation force, to mechanical pulling forceat a remote location.

It is a still further object of the present invention to provide asystem for actuation of the articulation section of aborescope/endoscope that minimizes the effective compressibility andelasticity of the actuating systems.

It is a still further object of the present invention to provide asystem for actuating the articulation section of a borescope that willoperate precisely and accurately over an extended distance from thecontrol apparatus to the distal end of the insertion tube without anyexternal power source.

The above and many other objects, features and advantages of thisinvention will become apparent from the ensuing description of apreferred embodiment which is to be considered in connection with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic and partial sectional view showing a borescopethat incorporates the hydraulic muscle pump of the present inventionwith a hydraulic dynamic muscle to actuate the articulation section ofthe borescope.

FIG. 2 is a partial sectional view on an enlarged scale of a pair ofhydraulic muscle pumps and a pair of hydraulic dynamic muscles showingthem in cooperative contracted and extended conditions, respectively.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

Referring now to FIG. 1 there is shown a borescope/endoscope 10embodying four hydraulic muscle pumps 12 according to the presentinvention with four hydraulic dynamic muscles 14 for actuating thearticulation section 16 of a borescope from a control 18. The borescope10 has an elongated flexible insertion tube 20 with a proximal end 22and a video imager head 24 disposed at its distal end. Adjacent the head24 is a steering or articulation section 16. This section is formed of anumber of spaced rings or discs and covered with a flexible sheath as iswell known in the art. This section has two pair 26 and 28 of steeringcables with one pair arranged for bending the articulation section in afirst plane and the other pair of cables bending the section in a planeperpendicular to the first plane. Each cable has a flexible sheath 30which carries the compressive reaction forces corresponding to thetensive force on the associated cable.

Four hydraulic dynamic muscles 14 are arranged in staggered fashionwithin the distal end of the insertion tube 20 adjacent the articulationsection 16 as was shown and described in the above patent. Eachhydraulic dynamic muscle 14 has an elongated flexible elastomericbladder or balloon 32 which is covered with a tubular braid 34 formed ofa number of fibers or filaments wound helically around the bladdercrossing at a braid angle of θ. A conduit or tube 36 extends from, theproximal end of each bladder through the insertion tube 20 to theproximal end 22 thereof. An anchor termination 38 seals the proximal endof both the bladder and braid to the distal end of the conduit 36. Asemi-rigid sheath 40 formed typically of a tube of synthetic resinextends distally from the anchor termination 38 and has a closed endthrough which extends the cable sheath 30 for either steering cable 26or for either steering cable 28. A forward or distal termination 42closes the distal end of the braid and connects the same to anassociated one of the steering cables 26 or 28.

A corresponding number of hydraulic muscle pumps 12 are positioned atthe proximal end of the insertion tube 20 adjacent the controller 18 forthe borescope/endoscope. Each of these hydraulic muscle pumps isconnected by a conduit 36 to a corresponding hydraulic dynamic muscle 14at the distal end of the insertion tube. Each hydraulic muscle pumpconsists of an elongated bladder or balloon 32' anchored at its distalend to a semi-rigid sheath 40' at 38' almost in mirror image to thehydraulic dynamic muscles at the distal end of the insertion tube. Theproximal end of each hydraulic muscle pump bladder is terminated andsealed at 42' about a cable 26' or 28' extending to the controller 18which typically has a pair of control knobs 44 and 46.

The system is connected as shown, and each individual hydraulic pump 12,conduit supply line 36, and hydraulic dynamic muscle 14 is filled with ahydraulic fluid and hermetically sealed as a unit.

The terms "liquid" and "hydraulic fluid" are used herein to denote anyliquid that is essentially non-compressible at its working pressure. Ihave found "Dow Corning 200 Fluid" brand of A Dimethylpolysiloxane to besatisfactory. Generally, the lower the viscosity of the liquid, thebetter the operation of my device. Also, it is important for someapplications that the liquid be non-toxic and as inert as possible.

Before sealing as a unit, one of the hydraulic dynamic muscle bladders32 is stretched to full length while the corresponding hydraulic musclepump bladder 32' is expanded to its full diameter for filling. Inoperation, the bladder at one end of a tube 36 will be in nearlyopposite condition to the bladder at the other end, depending on theactuation of the pair of muscles and pumps for each direction of motionof the articulation section of the borescope insertion tube.

Thus, as shown in FIG. 2, the hydraulic muscle pump 12-2 is in themaximum elongated condition and its corresponding hydraulic dynamicmuscle 14-2 is in the full expanded position. This pair provides onedirection of motion for the articulated section and its companion pair12-1 and 14-1 can be seen to be in the opposite condition, ready forrestoration of the bend of the articulation section 16 to neutral orreverse direction.

The hydraulic muscle pumps 12 are connected by cable pairs 26' and 28'to racks 48 and 50 at the control 18 such that, when it is desired tomove the articulated section in one direction, knob 44 is rotated tomove rack 48. The upper cable 26' is thereby pulled to elongate thebladder 32' to the condition shown in the top of FIG. 2. This compressesthe hydraulic fluid within the pump 12-2 and forces it out through thetube 36 to the hydraulic dynamic muscle 14-2 which expands to itsmaximum, and as it expands, it applies a tensive force to the cable 26connected to its end. The cable, in turn, pulls the articulation sectionof the borescope to bend it upwards. The opposite hydraulic pump 12-1and hydraulic muscle 14-1 for this plane of actuation are then in theexactly opposite condition, as shown, with the hydraulic muscle pump12-1 being in its fully expanded and foreshortened condition and thehydraulic dynamic muscle 14-1 being in the stretched condition. Thestretched condition is caused by the cable attached to the distal end ofits bladder being pulled by the bending of the articulation section ofthe borescope.

In order to bend the borescope in the opposite direction, the controlknob 44 will be operated to pull the bottom cable 26' to elongate theopposite bladder 32' in the hydraulic muscle pump 12-1. As it does thetension on the other cable 26' of the pair will be eased, allowing thebladder 32' in pump 12-2 to relax to its more normal expandedconfiguration. As the process continues muscle 14-1 is fully expandedand pulls on cable 26 to move imager head 24 in the opposite or downwarddirection and hydraulic fluid is forced from bladder 32 in hydraulicmuscle 14-2 to expand pump 12-2 and permit the tension applied to thecable 26 attached to muscle 14-1 to bend the articulated section 16 ofthe borescope in the downward direction as the bladder 32 in hydraulicdynamic muscle 14-1 is expanded and foreshortened.

In similar fashion, the other pair of hydraulic muscle pumps andhydraulic dynamic muscles not shown in FIG. 2 are actuated by thecontroller to move the distal end of the borescope insertion tube in aplane at ninety degrees to the plane of movement effectuated by thefirst pair.

It is thus seen that with this closed hydraulic system linking ahydraulic muscle pump and a hydraulic dynamic muscle, a completelyself-contained actuation system is provided that has virtuallyeliminated all the deficiencies of the prior art cable systems, whilemaintaining the small diameter of the insertion tube and the simplicityand direct actuation control of the cable systems. Since the hydraulicmuscle pumps function essentially in mirror image with the hydraulicdynamic muscles, good "feedback" is provided to the operator providingan appropriate and natural reaction to movement of the articulated endof the borescope. This force feedback to the operator improves theefficiency and accuracy of placement of the distal end of the borescopeand simplifies the training required for the operator while stillproviding a superior, more accurate hydraulic actuation of the imagerhead 24.

Since the characteristics of the hydraulic pump are analogous to thoseof the hydraulic dynamic muscle, at the start of a full cycle, the braidangle of the muscle pump braid surrounding the bladder is at itsgreatest and therefore, the required cable force for a given outputpressure is lowest and the motion of the pull is greatest. At the otherend of the cycle, the braid angle is at its smallest and the requiredcable force for the same output pressure is highest, and the motion ofthe pull is smallest.

As indicated above, each unit of hydraulic muscle pump, connectingconduit, and hydraulic dynamic muscle is hermetically sealed at alljunction points with the bladders, sleeves, conduit and actuating cablesto form one self-contained actuating element. This is an importantadvantage of this invention, particularly for endoscope applications,since it greatly reduces the risks of leakage and contamination. Also,the present invention has eliminated all "working" fluid seals in thesystem such as piston rings, packing glands, etc. Furthermore, the"friction" losses due to the bladders is a small percentage of thatencountered in usual cylinder/piston hydraulic or pneumatic systemswhich permits more sensitivity of control and/or greatly extendeddistance of control without loss of precision and accuracy. In oneembodiment of this invention, accurate manipulation has been obtained atover fifty feet of coiled insertion tube between the control and theviewing head.

Further, it should be understood that while the invention is shown withthe hydraulic pump muscle being a mirror image of the hydraulic dynamicmuscle and disposed within the insertion tube, some embodiments of thepresent invention may have the hydraulic pump muscle located outside ofthe insertion tube with a much larger diameter and shorter length, forthe same actuation capacity, than that shown in FIGS. 1 and 2.

In the preferred embodiment of this invention I have shown this closedhydraulic system as being used to actuate the articulation section of aborescope. It is believed apparent that this closed hydraulic systemcould be used for many other types of articulation requirements where aquantity of hydraulic fluid must be moved from one place to anotherthrough a connecting tube in order to actuate a device. Numerous roboticapplications of the closed actuation system of this device can bereadily visualized by those skilled in the art.

While the invention has been described in detail with reference to apreferred embodiment, it should be understood that the invention is notlimited to that precise embodiment, that many modifications andvariations thereof would present themselves to those skilled in the artwithout departing from the scope and spirit of this invention as definedin the appended claims.

What is claimed is:
 1. A hermetically sealed liquid actuation system fortransferring tensive linear motion from a local to a remote devicecomprising a first liquid dynamic muscle disposed at the distal end ofsaid actuation system, a second liquid dynamic muscle disposed at theproximal end of said liquid actuation system, and a tubular conduitconnecting said first and second muscles for transferring liquid fromone liquid dynamic muscle to the other each liquid dynamic musclecomprising:a semi-rigid tubular sheath; an elongated elastomeric bladderpositioned within said tubular sheath, a tubular braid member withproximal and distal ends disposed over said bladder within the saidtubular sheath, said braid formed of a plurality of flexible yetsubstantially inextensible filaments permitting said bladder therewithinto expand laterally when filled with liquid but restraining the bladdersuch that as said tubular braid increases in diameter, the braidcontracts axially, a liquid conduit hermetically sealed at one to saidbladder in said distal liquid dynamic muscle and at the other end tosaid bladder in said proximal liquid dynamic muscle; anchor means foranchoring one end of said tubular braid to one end of said tubularsheath of the distal liquid dynamic muscle; anchor means for anchoringone end of the sheath to one end of said braid at the proximal liquiddynamic muscle; a termination enclosing the other end of said tubularbraid at each of said proximal and distal liquid dynamic muscles; tendonmeans connected to said termination for carrying tensive force from saidbraid when said bladder and braid expand; and a flexible sheath memberdisposed about said tendon means for providing compressive reactionforces to said tensive force connected to the other one end of saidtubular sheath so that when a tensive force is applied to tendon meansat the proximal fluid dynamic muscle, a proximal bladder and tubularbraid is pulled to an elongated condition forcing liquid to the distalend of said liquid actuating system to cause the bladder and tubularbraid member therein to expand in diameter and contract axially to applya tensive force in an amount related to the distance the proximal tendonmember was pulled to thereby transfer the proximal tensive linear motionto the distal end of the hydraulic actuation system so as to provide anelongated flexible actuation system for transferring linear tensivemotion from an input actuator to a remote device.
 2. The method oftransferring tensive linear motion from a local location to a remotelocation which comprises:connecting a first elongated elastomericbladder member to one end of a hydraulic fluid conducting tube;connecting a second elongated elastomeric bladder member to the otherend of said hydraulic fluid conducting tube; positioning a tubularbraided enclosure member adapted to contract in axial length whenexpanded in diameter and vice-versa about said first and secondelastomeric bladder members, filling said hydraulic fluid conductingtube and elastomeric bladder members with hydraulic fluid, with onebladder in an expanded diameter condition and one bladder in anelongated condition; hermetically sealing said bladders and tube into aclosed system; and selectively applying a tensive force to one of saidbraid enclosed elastomeric bladders causing it to be longitudinallyextended to transfer hydraulic fluid and pressure to the other bladdercausing the other to expand in diameter radially and contract axially acorresponding amount to apply a tensive force at the remote location. 3.The method of claim 2 further defined by operatively connecting controlmeans to said first bladder member and articulation means to said secondbladder member.